I also recommend and use the 35 1.4 summilux and have found the optical RESULT (I won't argue formulas) vary with age of the lens. I have new lenses like my summilux and summicrons, both 50mm and 35mm that are 40 years old that definately have more of what I can render as the "Leica glow" as opposed to their newer models which, IMO, are sharper but not neccesarily better. Buying used is a very good idea and there are several dealors around who are of high quality and will give you a good deal.